Understanding the Role of Short Tandem Repeats (STRs)

Short Tandem Repeats (STRs)

Introduction

Short tandem repeats (STRs) are units of DNA composed of repeated sequences ranging from 1 to 6 base pairs (bp). They form a vital component of our genome, contributing significantly to genetic and phenotypic diversity across species. STRs play essential roles in evolutionary biology, genetic disorders, DNA profiling, and molecular marker studies.

Evolutionary Biology

Evolutionary forces shape the distribution of repetitive elements like STRs in genomes. These tandemly repeated sequences provide crucial insights into the mechanisms underlying genomic variation within species. Mutations in STR loci can lead to rapid contractions and expansions due to their high polymorphism rates, which is approximately 100 to 10,000 times more than other regions of the genome. Despite their high mutation rate, STRs serve as valuable markers for detecting evolutionary relationships between species.

Genetic Disorders

The most well-known aspect of STRs is their association with neurodegenerative repeat expansion diseases such as Huntington's disease. These diseases result from the expansion of normally stable short repeats to pathological lengths, leading to protein aggregation and cellular dysfunction. Other genetic conditions have been linked to STRs, including Wilson disease, myopathies, and certain types of cancer.

DNA Profiling and Forensics

STRs have been extensively used in forensic science for DNA profiling. They offer a high power of discrimination because the number of repetition units varies among individuals when assessed for identifying purposes. Digital DNA typing relies on these variations to differentiate individuals, providing critical evidence in criminal investigations. The selectivity and automation of polymerase chain reaction (PCR) techniques make STRs an ideal tool for generating profiles that can be compared to known samples found at crime scenes.